Device for measuring danger angle in navigation



E. STANWOOD, IR. DEVICE FOR MEASURING DANGER ANGLE IN NAVIGATION. APPLICATION FILED DEC, 18, 1919.

ama?" Patented 001:. 31, 1922.

2 SHEETS-SHEET lu H II I l I II I IIIH In E. STANWOOD, IR. DEVICE FOR MEASURINGDANGER ANGLE IN NAVIGATION.

APPLICATION FILED DEC. I3. I919.

Patented Oct. 31, 1922.

Z SHEETS-SHEET 2- Zhwam E7701 EaZ/MM W Jim/72 wm mdd Patented Oct. 31, 1922.

Davida 110a MaAsUBIk G DANGER ANGLE. IN. NAVIGATION- Application f led December 18, 1919. Serial No. 345,753.

at Wellesley, county of No folk, Commonwealth of Massachi setts, have inventedcer taln new and useful Improvements in Devices for Measuring Danger, Angle in Navigation, of which the following is a spccifica-' tion. v

This invention relates to a device for quickly determining the so-called danger angle in coast navigation.

' As far as Iain aware no. such device has ever been hereto or pro ide hi 'ang has usually been actually drawn with dividers on the chart itself, and then measured with theprotractors. This operation necessitates the drawing of a circle through three points and the consequent difficulty of finding the center. It furthermore is an operation which frequently must be performed under circumstances where accuracy is diflicult on account of storm and other causes and where haste is required. All these factors have tended to makethe use of the danger angle infrequent and little used, with the result that navigatorshave preferredto use cross bearings and the three-arm protractor and other methods. These are"in themselves good enough, but troublesome and complicated, although not as inconve n as the former me ho f d term ning the angle of danger.

A u rat v o my nvent eni I hav shown as mp e. orm o device h h I ha found well adapted to'practicalnavigation and one so simple, convenient and 'inexpen sive as to place it within the reach of all whether professional navigators, yachtsmen or students. Wh'le I shall discuss vention with particular reference to" the form shown, I am not'to be "understood as i in myse n n wa e ard to details of structure or manner 'of 1 use. Throughout the specification and drawings like reference characters are used toindicate c rrespondi g. par s, and in h drawings: Fig. I is. a plan viewpfmy str me Fig. II an illlStlflittlVe diag m s w ng old method of drawing in, and

Rigs. III and 1V illustrations of use of.

I my instrument for the same problem.

Before explaining 'th use of the device abov desc be tmay be onve e t t fi tefthe or g na m ne of e erm n ng th a l 0. d n e -f erstsfore it ha been cust mary n oa r ga i n upon approach of dangerous shoals or the like, to mark on the chart two shore points A'and B clearly visible and which will remain visible and clearly shown and correctly lo- ("rat ed on the chart. (See Fig. II.) I

It will be noted that the degree of separation of such points as A and B may vary widely under different circumstances. In addition to the shore points the navigator as obliged to establish a third point such as E offshore and beyond factorsof danger S which he is seeking to avoid. This point mus li i a' cir l su c e y arge nclude all factors of danger. In fact, it has always been deemed necessary to actually inscribe this circle through these three points order that the marg n of safety may be visually clear on thechartf I The'three points havingbeen selectedand the circle drawn the navigator had next to two chords thusinscribed' was then measured and the reading of this angle gave the so called of danger. By constantly taking sextant readings" on the two shore points the navigator was able to maintain a safe course with positive assurance as long as the sextant reading was not greater than the angl of danger u Obtained;

is Pr ctice n he s pp e tary usages for determining zones of safety between outlying rocks or shoals is set forth nf ooks o a g ota y n OW- ditch, page 64 to which referencema'y be made for further illustration of this method. In Fig; II, I have indicated this second point as G oif a shoal S and drawn in the inclusivecircle and chords.

' Inthe form of the instrument shown I provide a transparent disc 1 preferably of celluloid or like material." This is inscribed with" a series of concentric hands 2 preferablyetched or colored to differentiate one from another and to aid in'picking up the same circle in any part of the disc. On one side the disc is radially slotted as at 3 and t mlei t is t is ve ed a P Of a 16ers. o r vet d eemp s an ar yin 0' it u pe and afsemiev r enlar ment 6011 which is'a" scale T concentric"with the center of the rivet .45. The scale 7 is graduated in suitable degrees of arc" and is read from the adjacent edge 8 of the other pivoted member 8. The members 5 and '8 constitute straight edge chord arms for lay disc 1 to the face of the chart in the area in question. Bythe quick shifting of the con centric circles 2 over the face of the chart hey can immediately select that circle which "includes all of the danger area, making that circle pass through the two shore points'A and B. He can then locate on thesele'cted circle any, point such as E which in his judgement is most characteristic I of the danger of theparticularplace he is approaching. This point he covers bythe apex rivet 4 of his protractor arms, sliding. the free ends of said'arms 5 .an'dS to intersect the opposite side of the circle at the shore points. The danger angle'is then immediatelynand directly apparent from, the'protractor scale 7. This isallthat is required. The chart is not defaced. No linesflare drawn and thewhole result accomplished in a small fraction ofthetime previously required. Furthermore, where asecond reading is required, for a channel observationor for other places where the course must be held between two adjacent areas of danger, mydevlce may be slightly moved to bring a larger circle through the new third oroff shore point, G and the second angleestablished and read. The navigator is then safe to proceed, having only to watch the two shore points A and B and make sure that the sextant reading lies between his two danger angles. I

The importance of beingable to determine not only one, but as many danger angles asmay "e-required without difficulty and under the most adverse conditionscan not be over estimated. lVherever conditions have prevented the ready determination of such anglesor where they have been inconvenience and difliculty, unnecessary risks have been incurred with the all too frequent result of the loss of vessels and the consequent, loss of lives. j 7 What I therefore claim and desire to secure by Letters "Patent is: j I I 1 An instrument for determining a danger angle in navigation, comprising a memberhaving a p vot and an area of reference in cir'cles of diflerent radii, a pair of arms mounted on said disposable in variable positions of chord included angle of disc tric circles, and. a pair of' arms mounted on able in said slot, 7 H "said pivotfor'determining the included angle of are between two across "said area of reference, and a scale concentric with the pivot of said arms and in "referable relation thereto.

2. An instrument for determining a danger angle in navigation, comprising a transparent iii'ernber having a pivot and a plurality of concentric circular markings, a pair of arms mounted on said pivot and movable radially of said. member and having edges disposable in variable positions of chord across said circular markings, and a scale concentric with"the pivot of said arms and in referable relation thereto. An instrument for determining a dange'rangle in navigation, comprising a transparent member having a'pivot and a plurality of differentiated concentric circular markings, a pair of arms mounted on said pivot and movable fradially of said member and having edges disposable in variable positions o f chord across said circular markings, and a scale concentric with the pivot ofsaid arms and in referable relation thereto. Y

4; In a device of thejclassdescribed, a disc having a pivot and a series of concen- 'tric circles, and a pair of arms mounted on said pivot and radially adjustablerelative'to the center of said disc for determining the are between two points on the periphery of any circle;

5. Ina deviceof the class described, a

having: a DlVObaIlCl a series of'concensaid pivot and radially adjustable relative to the center-jot said disc for determining the included angle of are between two points on the periphery of an circle;

6. In a device the class described, a disc having a series of concentric circles, a pair of pivoted armsradiall adjustable relative to the center "of said disc for determiningthe included angle of are between two points on the peripheryof any circle,

and a scale in referable relation to saidarms and concentric with the pivot therefor. j 7. In a device of the class descrlbed, a disc having a series of concentrlc circles and having a radialslot, a pivot adjustableinsaid slot, and a'pair or arms mounted on v said pivotfor determining the included neglectedby navigators on account of the' disc having a series of concentric circles and having a radial slot, a pivot 'adjusta pair of arms mounted on ci i he ripheryof any cir'cle,,anda scalein 'referable relation to'said'arms and concentric with thepivot'therefor. v p vot and movable i i i radially of sa d member and having edges 9. "In a device of the, class described, a disc having aseries of concentric circles, a

pair of arms pivoted on said disc for determinin the included angle or are between 7 two POlIlllS on the periphery of any circle,

one of said arms extended as a scale, and said scale concentrlc wlth the pivot for the arms.

10. In a device of the class described, a disc having a series of concentric circles and having a radial slot, a pivot adjustable in said slot, an arm mounted on said plvot and having a radially disposed portion and a circular portion, said circular portion concentric With said pivot and having scale markings, and a second arm cooperative with said first-named arm.

11. In an instrument of the class described, a disc having a plurality of concentric circles, an arm pivotally and slidably mounted on said disc and having an offset portion provided with scale markings, and a second arm mounted on the pivot for the first-name arm and readable with relation to the scale markings of saidofi'set portion.

12. In an instrument of the class de-, scribed, a disc having concentric circles, an arm pivotally mounted on said disc for movement radially of said circles and havportion provided I mounted on'the pivot for the said first named arm and readfible with relation to the scale markings of said arcually curved portion.

13. In an instrument of the class described, a disc having concentric circles, an arm pivoted to said disc and movable radially of said circles an having a scale portion disposed concentric to the pivot for said arm, and a second arm mounted on said pivot and readable with relation to said concentric scale portion. I

14. In an instrument of the class described, a disc having a plurality of concentric circles, an arm plvotally and slidably 'mounted on said disc and having an ollset portion provided with scale markings,

and a second arm mounted on the pivot for said first-named arm and readable with relation to the scale markings of said ofiset portion. I

In testimony whereof I a-fiix my signature.

EDWARD STANWOOD, JR. 

